diff --git a/fs/fat/fat.c b/fs/fat/fat.c
index c1e5741..49c78ed 100644
--- a/fs/fat/fat.c
+++ b/fs/fat/fat.c
@@ -352,7 +352,7 @@
 			newclust = get_fatent(mydata, endclust);
 			if((newclust -1)!=endclust)
 				goto getit;
-			if (newclust <= 0x0001 || newclust >= 0xfff0) {
+			if (CHECK_CLUST(newclust, mydata->fatsize)) {
 				FAT_DPRINT("curclust: 0x%x\n", newclust);
 				FAT_DPRINT("Invalid FAT entry\n");
 				return gotsize;
@@ -387,7 +387,7 @@
 		filesize -= actsize;
 		buffer += actsize;
 		curclust = get_fatent(mydata, endclust);
-		if (curclust <= 0x0001 || curclust >= 0xfff0) {
+		if (CHECK_CLUST(curclust, mydata->fatsize)) {
 			FAT_DPRINT("curclust: 0x%x\n", curclust);
 			FAT_ERROR("Invalid FAT entry\n");
 			return gotsize;
@@ -459,7 +459,7 @@
 
 		slotptr--;
 		curclust = get_fatent(mydata, curclust);
-		if (curclust <= 0x0001 || curclust >= 0xfff0) {
+		if (CHECK_CLUST(curclust, mydata->fatsize)) {
 			FAT_DPRINT("curclust: 0x%x\n", curclust);
 			FAT_ERROR("Invalid FAT entry\n");
 			return -1;
@@ -652,7 +652,7 @@
 	    return retdent;
 	}
 	curclust = get_fatent (mydata, curclust);
-	if (curclust <= 0x0001 || curclust >= 0xfff0) {
+	if (CHECK_CLUST(curclust, mydata->fatsize)) {
 	    FAT_DPRINT ("curclust: 0x%x\n", curclust);
 	    FAT_ERROR ("Invalid FAT entry\n");
 	    return NULL;
diff --git a/include/fat.h b/include/fat.h
index 92638d5..f993cca 100644
--- a/include/fat.h
+++ b/include/fat.h
@@ -111,7 +111,8 @@
 #define START(dent)	(FAT2CPU16((dent)->start) \
 			+ (mydata->fatsize != 32 ? 0 : \
 			  (FAT2CPU16((dent)->starthi) << 16)))
-
+#define CHECK_CLUST(x, fatsize) ((x) <= 1 || \
+				(x) >= ((fatsize) != 32 ? 0xfff0 : 0xffffff0))
 
 typedef struct boot_sector {
 	__u8	ignored[3];	/* Bootstrap code */